drm/i915/psr: Add some documentation of variables used in psr code

We are adding more boolean variable into intel_psr and intel_crtc_state
structs. Add some documentation about these for sake of clarity.

v2: Modify has_psr +  has_panel_replay to mean panel replay
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240405113602.992714-2-jouni.hogander@intel.com

drivers/gpu/drm/i915/display/intel_psr.c

@@ -171,6 +171,22 @@
  *
  * The rest of the bits are more self-explanatory and/or
  * irrelevant for normal operation.
+ *
+ * Description of intel_crtc_state variables. has_psr, has_panel_replay and
+ * has_sel_update:
+ *
+ *  has_psr (alone):					PSR1
+ *  has_psr + has_sel_update:				PSR2
+ *  has_psr + has_panel_replay:				Panel Replay
+ *  has_psr + has_panel_replay + has_sel_update:	Panel Replay Selective Update
+ *
+ * Description of some intel_psr varibles. enabled, panel_replay_enabled,
+ * sel_update_enabled
+ *
+ *  enabled (alone):						PSR1
+ *  enabled + sel_update_enabled:				PSR2
+ *  enabled + panel_replay_enabled:				Panel Replay
+ *  enabled + panel_replay_enabled + sel_update_enabled:	Panel Replay SU
  */
 
 #define CAN_PSR(intel_dp) ((intel_dp)->psr.sink_support && \